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#### Question 1:

Write the proper words in the blanks.
(meridian, horizon, twelve, nine, apparent, celestial, ecliptic)

(a) When seen from a great distance, the sky seems to be touching the ground along a circle. This circle is called the ............. .

(b) The .............  is used while defining the zodiac signs.

(c)  Classified according to seasons, one season will have .............. nakshatras.

(d) The rising of the sun in the east and its setting in the west is the .................. motion of the sun.

(a) When seen from a great distance, the sky seems to be touching the ground along a circle. This circle is called the horizon.

(b) The ecliptic is used while defining the zodiac signs.

(c)  Classified according to seasons, one season will have nine nakshatras.

(d) The rising of the sun in the east and its setting in the west is the apparent motion of the sun.

#### Question 2:

A star rises at 8 pm tonight. At what time will it rise after a month? Why?

The star will rise at 6 pm after a month. This is because each star rises or sets 4 min earlier everyday. Thus, in a month, the total advancement in the rising time of a star =
So, if a star rises at 8 pm today, it will rise before 2 h i.e. at 6 pm after a month.

#### Question 3:

What is meant by 'The sun enters a nakshatra' ? It is said that in the rainy season the sun enters the Mrug nakshatra. What does it mean?

A constellation or nakshatra is present behind the Sun, which gets hidden because of the bright sunlight. So, when we look up in the sky, we are actually seeing both the Sun and the constellation behind it. Thus, when the Earth changes position, it appears to an observer on Earth, as if the Sun has moved from its position and is entering a new constellation or nakshatra.
The Sun entering the Mrug nakshatra in rainy season means that Mrug nakshatra or Orion is behind the Sun.

#### Question 4:

Answer the following question.

(a) What is a constellation?
(b) What points should be considered before a sky watch?
(c) Is it wrong to say that the planets, stars and nakshatras affect human life? Why?

(a) A group of stars forming a definite shape is known as constellation. Few examples of constellations are Orion, Big Dipper.

(b) The points to be considered before doing skywatch are:

• The place chosen for skywatching should as far as possible from the city.
• The night chosen for skywatching should be new moon night.
• Binoculars or telescopes should be used for skywatching.
• Pole Star should be chosen as a reference point for skywatching.
• Skywatching should begin with stars in west.

(c) Yes, it would certainly be wrong to say that planets, stars and nakshatras affect human life. This is because till now there is no credible evidence supporting astrology. Science, as we know, does not follow beliefs but has its basis on observations and evidences. Thus, it has rejected the thoughts and beliefs of many that the planets, stars and nakshatras affect human life .

#### Question 5:

Write a paragraph on the birth and lifecycle of stars using figure 20.1.